Bulky composite stretch yarn



G. v. LUND ETAL 3,146,575

BULKY COMPOSITE STRETCH YARN Sept. 1, 1964 Filed Aug. 14, 1961 United States Patent 3,l46,575 Patented Sept. 1, 1964 "ice 3,146,575 BULKY COMPOSITE STRETCH YARN Geoffrey V. Lund, Daphne, and Robert D. Smith, Mobile, Ala, assignors, by mesne assignments, to Courtaulds Limited, London, England, a company of Great Britain Filed Aug. 14, 1961, Ser. No. 131,119 6 Claims. (Cl. 5714ti) This invention relates to an elastic yarn and to methods for making such yarn.

In recent years there has arisen a demand for stretch yarns, i.e., yarns which, without any elastomeric component, have a high degree of recoverable stretch. Such yarns are normally multi-ply yarns in which the stretch iness is obtained by controlling the twist given to the variout component yarns.

It has also been proposed to make bulky yarns by blending thermoplastic and non-thermoplastic fibers and then heating the blend. On heating, the thermoplastic fibers shrink, causing the yarn to be shortened in length and the non-thermoplastic fibers to be folded upon themselves. Although such yarns are bulky, i.e. of increased diameter, they are not stretchy. When pulled out, they recover their original length only to a very limited extent.

The present invention provides a new type of yarn which is both bulky and stretchy. In accordance with the invention, a yarn is provided which comprises thermoplastic fibers and cross linked cellulosic filamentary material in which at least a major portion of said cross linked cellulosic fibers have a memory, rendered permanent by the cross linking, for a physical position in which the individual filaments are buckled or folded under themselves. Such composite yarns are made, in accordance with the invention, by blending thermoplastic filamentary material with cellulosic filamentary material, heating the resulting yarn to shrink the thermoplastic filamentary material, thus folding the cellulosic material upon itself, and cross linking the cellulosic material.

In the drawing:

FIG. 1 shows schematically a yarn in accordance with the invention, before heating; and

FIG. 2 shows schematically a yarn in accordance with the invention after heating and cross-linking.

Referring to FIG. 1, a yarn 1 for use in the invention comprises cellulosic fibers 2 and thermoplastic fibers 3. After heating and cross-linking the yarn 1 is bulked (as shown in FIG. 2), the thermoplastic fibers 3 being shortened and the cellulosic fibers 2 being folded upon themselves.

The thermoplastic filamentary material used in the present invention may be any thermoplastic filaments which shrink when heated. Polyolefin fibers such as polyethylene or polypropylene fibers are particularly suitable but other similar materials can be used such as nylons, polyesters, e.g. polyethylene terephthalate, vinyl chloride, vinyl acetate, acrylontrile, acrylic ester and cellulose ester, e.g., cellulose acetate fibers. Preferably the thermoplastic filamentary material is present in the yarn as staple fiber. The denier of the thermoplastic filaments is not critical and will, of course, vary with the composition of the filaments, but will usually be from about 1.5 to about 15.

The cellulosic filamentary material may be natural cellulosic fiber such as cotton, linen, jute, sisal and hemp, or it may be regenerated cellulose in which case it may be made by any desired process, e.g. by the viscose, cuprammonium, nitrate processes or by the saponification of cellulose esters such as cellulose acetate. Preferably staple fiber is used. The denier of the filaments may again vary widely but will usually be from about 1.5 to about 15.

The cellulosic filamentary material may be cross linked by any of the reagents known to the art. These include formaldehyde, dialdehydes such as glutaraldehyde and adipaldehyde, hydroxy aldehydes such as hydroxyadipaldehyde, mixed aldehydes such as acrolein, glycidyl aldehydes; the so-called reactant type resins, for example modified urea resins, i.e. methylol compounds such as methylated methylol urea, partially polymerized methyl ated methylol urea, methylated and unmethylated methylol ethylene ureas, such as dimethylol ethylene urea, and methylated and unmethylated methylol 1,2-propylene ureas, as well as dimethylol triazines, triazones, and the like; polyacetals (including diacetals) of polyhydroxy compounds, for example, the products described in Patent No. 2,786,081; divinyl sulfone; dihalohydrines, for example, dichlorohydrin; and diand tri-aziridinyl phosphine oxides and sulfides as described in Patent No. 2,859,124.

Still other cross linking agents in common use and which may be employed in the present invention are the heat hardenable resins. These include the aminoplasts which may be defined as heat hardenable condensation products of compounds having at least two amino hydrogens, with methylol forming compounds. Typical aminoplasts are urea-formaldehyde, melamine formaldehyde, dicyandiamide formaldehyde, guanadine formaldehyde and combinations of these. The term is also used to include the methylol-amino-epihalohydrin compounds described in Daul Patent No. 2,960,484. Other resinous cross linking agents include those formed by the reaction of formaldehyde and acrolein as described in Patent No. 2,696,477; resins formed by the reaction of acetone and formaldehyde as described, for example, in United States Patents Nos. 2,504,835 and 2,711,971; and polyepcxy resins, e.g. polyfunctional compounds having at least two epoxy groups linked through a hydrocarbon, a polyhydric phenol or a polyhydric alcohol group, such as the resins formed from saturated polyglycidyl ethers of polyhydric alcohols as described in Patent No. 2,752,269. Particularly interesting compounds of this last named group are the condensation products of epichlorohydrin with ethylene glycols.

It will be clear that the precise nature of the cross linking agent is not a part of the invention. Of the various agents listed above, formaldehyde and dimethylol ethylene urea will be found especially useful.

In practicing the invention, various manipulative sequences can be used. Where both the thermoplastic and the cellulose filamentary materials are staple fiber they may be blended before spinning on conventional textile machinery. For example, both cotton and rayon yarns are conventionally made using the well known cotton system of spinning. In this the fiber is taken from the bale, and run through a picker to form a lap. The lap is delivered to a carder. The carder fibers may be combed and are then drawn, slubbed, and spun. In making yarns according to the invention the blending is preferably carried out in the picker, i.e. by adding the thermoplastic fibers to the cellulosic fibers as the latter are bing processed in the picker. This insures maximum dispersion. However, the mixing can take place at any convenient place prior to spinning. Moreover, it is obvious that other systems than the cotton system may be employed.

The proportions of the thermoplastic and cellulosic yarns which are blended are open to considerable variation, and depend on the type of fibers being used and on the relative denier of the two fibers. An overall range (percent by weight) would be from about 25% cellulose and about thermoplastic to about cellulose and about 5% thermoplastic. Preferably the blends will contain (by weight) from about 5% thermoplastic and 95% cellulose to about 35% thermoplastic and about 65% cellulose.

The cross linking agent may be present in the cellulose fiber at the time of blending. However, cross linking of the cellulose must not take place until after the fibers have assumed their folded positions. Hence care must be taken that the combination of cross linking agent and curing agent used is such that premature curing does not take place. In most cases it is preferable to impregnate the blended yarn with curing agent and since in most cases shrinking of the yarn will require a temperature at least equal to the curing temperature of the cross linking agent, it is preferred to impregnate the yarn after it has been shrunk.

Shrinking of the yarn is carried out by simply heating the yarn in a relaxed condition. The temperature required will of course depend on the nature of the thermoplastic fiber and can range from say 70 to 250 C. Any suitable heating apparatus may be employed.

In impregnating the yarn, various manipulative procedures may be used. Conveniently, the yarn may be passed through a bath of the agent or the yarn or a bundle of yarns may be laid down in a plaited pattern on a moving belt and subjected to a spray or bath of a liquor containing the reagent.

The concentration of the cross linking agent in the treating liquor will of course depend on the amount of cross linking it is desired to effect, on the composition of the yarn and On the efiiciency of the cross linking agent. In general it should be such as to deposit on the yarn between about 0.1 and about 15% cross linking agent, based on the dry weight of cellulose in the yarn.

After the yarn has been impregnated, it may be dried at a temperature of say 120 to 150 C. and cured at a temperature which will depend on the cross linking agent used, but which will in general range between about 150 C. and about 190 C. If desired, drying and curing may be carried out simultaneously. The yarn should be in a relaxed condition during both drying and curing.

If desired, impregnation may be carried out before shrinking, and shrinking and curing effected simultaneously. However, in general the results are not as satisfactory as when the yarn is fully shrunk prior to curing.

The invention will be further described with reference to the following specific examples which are given for purposes of illustration only and are not to be taken as in any way limiting the invention beyond the scope of the appended claims.

EXAMPLE 1 A yarn containing 25% by weight 2 inch, 3 denier polypropylene staple fiber and 75% 2 inch, 3 denier viscose rayon staple fiber is prepared using the cotton system, by adding both the polypropylene staple and the rayon to the picker. The yarn is then treated with an aqueous solution containing, by weight, dimethylol ethylene urea and 3% lvigCl -6H O. It is padded to 100% pickup, dried at about 80 C. and heated at 160 C. for 3 minutes to effect curing and shrinkage simultaneously. A shrinkage of 10% is observed. Samples of the yarn each ten inches long are then loaded with various weights and the stretch measured. The weights are then removed and the recovery measured. The results are given in Table A below:

Table A Percent Percent Load, grams I Stretch 1 Recovery EXAMPLE 2 The yarn used in Example 1, containing 25% by weight 2 inch, 3 denier polypropylene staple fiber and by weight 2 inch, 3 denier viscose rayon staple fiber is heated at 160 C. without impregnation with cross linking agent. A shrinkage of 26% is observed. The bulky yarn so obtained is treated with an aqueous solution containing 10% by weight dimethylol ethylene urea and 3% MgCl .6H O, padded to 100% pickup, dried at about C., and cured for three minutes at 160 C.

Samples ten inches long are again weighed, and stretch and recovery measured. The results are shown in Table B below:

Table B Percent Percent Load, grams Stretch Recovery It will be observed that when shrinkage is completed before cross linking, heigher stretch and elastic recovery are obtained than when stretching and curing are carried out simultaneously.

EXAMPLE 3 The yarn used in Examples 1 and 2 is heated to 160 C. to etfect a shrinkage of 26% and then impregnated with an aqueous solution containing 3% HCHO and 3% MgCl .6H O. It is padded to pickup, dried at 80 C. and heated to C. for 3 minutes to effect curing. A bulk yarn having excellent elastic recovery is obtained.

EXAMPLE 4 Table C Percent Recovery Percent Load, grams Stretch ROD-INNIOH UrwNmOtn The foregoing examples shown clearly that cross linking the cellulose establishes a memory in the cellulose for its folded, contracted position and greatly enhances the elastic properties of the yarn.

We claim:

1. A bulky, stretchy, composite yarn of thermoplastic fibers and cross linked cellulosic fibers, at least a major portion of said cross linked cellulosic fibers having a memory, rendered permanent by said cross linking, for a physical position in which they are folded upon themselves.

2. The yarn claimed in claim 1 wherein the cellulosic fibers are rayon fibers.

3. The yarn claimed in claim 1 wherein the thermoplastic fibers are polyolefin fibers.

4. The yarn claimed in claim 3 wherein the thermoplastic fibers are polypropylene fibers.

5. The yarn claimed in claim 1 wherein the cellulose fibers are cross linked by means of an agent selected from the group consisting of formaldehyde and dimethylol ethylene urea.

6. A bulky, stretchy, composite yarn of thermoplastic fibers and cross linked cellulosic fibers, said yarn being capable of assuming an extended position and a relaxed position, and cellulosic fibers being folded upon themselves when said yarn is in the relaxed position and when said yarn is extended, retaining a memory rendered permanent by said cross linking, for the position in which they are folded upon themselves.

References Cited in the file of this patent UNITED STATES PATENTS 6 Harris et a1. Apr. 18, 1950 Bloch Feb. 8, 1955 Miller Sept. 10, 1957 Stuewer et a1. Sept. 29, 1959 Sonnino Nov. 22, 1960 Weldon May 30, 1961 Becker et al. Nov. 7, 1961 Moler Nov. 7, 1961 Pitts Nov. 14, 1961 Lund June 19, 1962 FOREIGN PATENTS Great Britain Sept. 16, 1942 Great Britain Sept. 16, 1942 

1. A BULKY, STRETCHY, COMPOSITE YARN OF THEMOPLASTIC FIBERS AND CROSS LINKED CELLULOSIC FIBERS, AT LEAST A MAJOR PORTION OF SAID CROSS LINKED CELLULOSIC FIBERS HAVING A MEMORY, RENDERED PERMANENT BY SAID CROSS LINKING, FOR A PHYSICAL POSITION IN WHICH THEY ARE FOLDED UPON THEMSELVES. 